create vg with same name as exported vg

i have run into a situation where lvm2 does not behave the same as lvm1. basically i want to be able to create a vg with the same name as an exported vg.

in lvm1 (v1.0.3) is was able to export the vg and create a vg with the same name on a different pv. the original "vgturner4" was on /dev/hda6.

# vgchange -a n vgturner4
# vgexport vgturner4
# pvcreate -ff /dev/hda7
# vgcreate vgturner4 /dev/hda7

in lvm2 (v2.00.07) it complained that there was already a vg with that name. the original vg was on /dev/sdc.

# vgchange -a n vg1
# vgexport vg1
# pvcreate -ff /dev/sda
# vgcreate vg1 /dev/sda
  A volume group called 'vg1' already exists.

a "vgscan" in lvm1 returns:

# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- found active volume group "vg0"
vgscan -- found active volume group "vgturner4"
vgscan -- found active volume group "vg0m"
vgscan -- found exported volume group "vgturner4PV_EXP"
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume
groups

a "vgscan" in lvm2 returns:

# vgscan
Reading all physical volumes.  This may take a while...
  Found exported volume group "vg1" using metadata type lvm2

i notice that the exported vg in lvm1 is actually renamed but in lvm2 it retains its original name. any ideas on how to accomplish what i want to do in lvm2?

rich turner

is this a bug within lvm2, is it no longer possible with lvm2, or is there a different procedure to accomplish this?

The LVM2 tools get confused if they see 2 VGs (1 live, 1 exported) with the same name. It is not trivial to change to tools to cope with this, so for now, you should avoid getting into this situation. [If necessary, use lvm.conf filters to hide the exported PVs while you rename the live VG to something else.]

Alasdair

[email protected]

LVM1 actually handled this very well. With LVM1 it would rename the VG, appending "PV_EXP" to the VG name when exporting it. This essentially would allow creating a new VG with the same original name. I am kind of surprised this did not carry over to LVM2.

I understand that the easiest solution would be to not be in this situation. Unfortunately, my company develops disaster recovery software that allows users to create/re-create/migrate LVM disk configuration. We need to be very careful about how we detect and create PV's/VG's.

LVM2 still does that for lvm1-format VGs of course. And for lvm2-format VGs it simply sets a flag in the metadata to say it's exported.

No, the issue is that LVM2 is using the not-guaranteed-to-be-unique VG name internally in places where it ought to be using the unique VG uuid.

And vgimport should work by VG uuid (in case there are several exported VGs present all with the same name) and require a new post-imported name to be specified if there's already a live VG with the same name.

Alasdair

[email protected]